Pseudocoelomates : Round Worms Chapter 11

Round Worms 2 Main Phlya – Nematoda “thread worm” ex: hookworms, pin worms, ascaris, filarial worms – Rotifera “wheel -bearer”

Phylum Nematoda Species: ~16,000 One of the most abundant animals on Earth – 5 Billion per Acre of Fertile Garden Soil Food: Organic Matter Many are Parasitic Tissue of Animals & Plants Rotting Substances Recycle nutrients in soils & bottom sediments

Phylum Nematoda Reproduction Sexual Sperm is amoeboid Dioecious – males and females separate Males smaller than females (dimorphic) 100s -1000s of eggs per day Lifestyles: Mostly parasitic Some free-living

Phylum Nematoda Digestive Tract Complete digestive tract Mouth surrounded by lips – that have sensory organs Mouth, teeth, jaws, buccal ‘mouth’ cavity, pharynx, intestines, rectum, anus

Phylum Nematoda Excretory System/Waste Removal 1 or 2 renette cells – glands absorb wastes from pseudocoelom and empties them outside through a excretory pore Osmoregulation of Nitrogen: – Ammonia & Urea

Phylum Nematoda Body: Size: microscopic – several meters Molt their cuticle Body wall has only longitudinal muscles Triploblastic Bilateral symmetry Unsegmented Pseudocoelomate

Phylum Nematoda Nervous System Anterior nerve ring Neuroendocrine secretions (hormones) – Growth, molting, cuticle formation, metamorphosis

Phylum Rotifera

Species:~2,000 Ciliated corona surrounding mouth Muscular pharynx (AKA Mastax) – Jaw-like function – Parthenogenesis is common Unfertilized egg develops into a new individual Freshwater or Marine Size: Very small! mm